Install the heat pump in By-pass (on a circuit derived from the main one). This way, when it needs to be disconnected, it can be done without problems to the pool water recirculation;
Check that it has a COP of at least 4;
COP or the coefficient of performance of the heater. A COP of 4 means that the pump "returns" 4 times more heat than the electrical power absorbed;
To choose the heat pump you can use this indicative formula: Pool volume x temperature difference between starting and desired temperature x 1.16 (fixed coefficient). This indicates the QE (quantity of energy in kw). If there is a thermal cover, add + 20% to the kw obtained. Without thermal cover, multiply by 2. Now calculate the time it takes for the heat pump to heat the pool: QE7P which is the rated power of the heat pump. The result is the number of hours needed to reach the desired temperature.
Install the heat pump in full sun;
Check that it can work with salt electrolysis if you have this disinfection system;
Install the heat pump in an "open" area. With good air circulation. The heat pump "discharges" cold air, if there is no possibility of recirculation it will go into block;
Check the flow rate of the pool system before purchasing the heat pump. Each pump requires a minimum flow rate to function properly;
Exclude it from the main recirculation during shock treatments;
For winter, or periods of non-use, wash the circuit in which the pool water flows with mains water.